Valve plate for a compressor

ABSTRACT

A valve plate for a compressor, a compressor, and a method of thermal insulation applied in a compressor. The valve plate has a thermally insulating capability for thermally insulating a suction muffler of the compressor from a discharge plenum in a cylinder head of the compressor.

FIELD OF INVENTION

The present invention relates generally to valve plate for a compressor,a compressor, and to a method of thermal insulation applied in acompressor.

BACKGROUND

Gas-compression refrigeration has been and still is the most widely usedmethod for fridges and air-conditioning of large public buildings,private residences, hotels, hospitals, theatres, restaurants andautomobiles etc. The gas-compression refrigeration system uses acirculating refrigerant as a medium, which absorbs and removes heat froma location or space to be cooled and subsequently dissipates the heatelsewhere.

A typical gas-compression system has four components: a compressor, acondenser, an expansion valve (also called a throttle valve), and anevaporator. The compressor sucks low-temperature and low-pressuresaturated gas from the evaporator and compresses the gas tohigh-pressure, resulting in higher temperature as well. To improve thevolumetric and energetic efficiencies of the compressor, which is todraw larger volume of the gas within a compressor's single compressioncycle, it is desired to thermally insulate the drawn low-temperature gasin the suction line from hotter parts of the compressor so that thelow-temperature gas from the evaporator can be pumped in larger volumewhen its temperature is kept low. One of the major causes responsiblefor heating the internal components of the compressor is its dischargesystem, as the refrigerant gas reaches its highest temperature levelsduring the compression cycle. The heat generated by the compression isdissipated to other components of the compressor.

There are many components along the suction line. These componentsinclude a muffler, a cylinder head, and some pipelines, etc. Inside acommonly adopted reciprocating compressor for a refrigeration system,the muffler is usually provided inside the compressor shell at a gassuction side for conducting the received gas to a suction valve of thecompressor. The valve, with its valve plate, is the interface betweenthe suction and discharge gas.

However, it is difficult to prevent heat exchange between thelow-temperature gas and other hotter parts of the compressor because thedrawn gas is present in the compressor within a narrow space and shortdistances from the hotter parts of the compressor. One approach is toimprove thermal insulation for the storage or interface medium of thesuction gas. These mediums can be manufactured from materials of lowthermal conductivity, such as resins or plastics. Recently, there arealso some structural approaches to improve thermal insulation of themuffler.

One suction muffler suggested in WO02/101239A1 has designed two acousticchambers for refrigerant gas communication inside a muffler. Inparticular, a first acoustic chamber of the muffler, which directlyreceives low-temperature gas outside the compressor, is surrounded by asecond acoustic chamber of the muffler. This structure providesadditional thermal insulation to the received low-temperature gas in thefirst acoustic chamber because heat flow from the exterior has to crosssurrounding walls of the second acoustic chamber to reach thelow-temperature gas inside the first acoustic chamber. However, thedesign of two acoustic chambers complicates the internal structure ofthe muffler and increases the muffler's size which also adverselyaffects the manufacturing cost of the muffler. Furthermore, thestructural strength and reliability of the muffler may be compromised.

A need therefore exists to provide solution for a refrigeration systemthat seeks to address at least one of the above problems.

SUMMARY

In accordance with a first aspect of the present invention there isprovided a valve plate for a compressor, the valve plate having athermally insulating capability for thermally insulating a suctionmuffler of the compressor from a discharge plenum in a cylinder head ofthe compressor.

The valve plate may comprise a first plate element made from thermallyinsulating material and a second plate element made from metal.

The first and second plate elements may be joint by one or more of agroup consisting of press-fitting, injection molding, induction heating,bonding adhesive, and ultrasonic welding.

The first plate element may be disposed to face the discharge plenum.

The valve plate may further comprise a third plate element made frommetal, and the first plate element is sandwiched between the first andsecond plate elements.

The first, second and third plate elements may be joint by one or moreof a group consisting of press-fitting, injection molding, inductionheating, bonding adhesive, and ultrasonic welding.

The first plate element may be configured to be received in a recessformed in the second plate element.

The recess may be formed around a suction orifice in the second plateelement.

The second plate element may comprise a raised portion around adischarge orifice in the second plate element, and the first plateelement comprises an opening for receiving the raised portion.

The valve plate may comprise a first plate element made from thermallyinsulating material and a metal coating on one or both sides of thefirst plate.

In accordance with a second aspect of the present invention there isprovided a compressor comprising a valve plate as defined in the firstaspect.

In accordance with a third aspect of the present invention there isprovided a method of thermal insulation applied in a compressor,comprising using a valve plate having a thermally insulating capabilityfor thermally insulating a suction muffler of the compressor from adischarge plenum in a cylinder head of the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be better understood and readilyapparent to one of ordinary skill in the art from the following writtendescription, by way of example only, and in conjunction with thedrawings, in which:

FIG. 1 shows a schematic diagram illustrating a temperature profile of arefrigerant gas path inside a reciprocating compressor;

FIG. 2 shows schematic drawings illustrating heat flow from hightemperature discharge gas to the suction path at the suction anddischarge interface, using (a) a conventional valve plate and (b) anvalve plate structure according to an example embodiment.

FIG. 3 shows a schematic drawing of a compressor according to an exampleembodiment.

FIG. 4 shows a schematic drawing illustrating a valve plate structureaccording to an example embodiment.

FIG. 5 shows a schematic drawing illustrating a valve plate structureaccording to an example embodiment.

FIG. 6 shows a schematic drawing illustrating a valve plate structureaccording to an example embodiment.

FIG. 7 shows a schematic drawing illustrating a valve plate structureaccording to an example embodiment.

FIG. 8 shows a schematic drawing illustrating a valve plate structureaccording to an example embodiment.

FIG. 9 shows a schematic drawing illustrating a valve plate structureaccording to an example embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, the interior of a compressor 100 for hermeticgas-compression refrigeration is exposed for indicating a temperatureprofile of a refrigerant gas along its travelling path inside thecompressor 100. The present invention is applicable to both Hermetic andsemi-hermetic compressors. As will be appreciated by a person skilled inthe art, the difference between the hermetic and semi-hermeticcompressors is that the hermetic compressors use a one-piece weldedsteel casing that cannot be opened for repair. A semi-hermeticcompressor uses a large cast metal shell with gasketed covers that canbe opened to replace motor and pump components.

The compressor 100 comprises a suction inlet pipeline 102, a suctionmuffler 104, and a cylinder head 108. The suction muffler 104 isdisposed inside the shell 106 of the compressor 100. The suction muffler104 connects to the cylinder head 108 which has a suction plenum 116 anda discharge plenum 114 at its interior. The suction plenum 116 receivesthe gas with lower temperature while the discharge plenum 114 receivesthe compressed gas from the cylinder chamber (hidden) at highertemperature. The suction plenum 116 and the discharge plenum 114 areconnected to a cylinder chamber (hidden) via a suction valve and adischarge valve (not shown) respectively. The discharge plenum 114 isfurther connected to the discharge pipeline 118 of the compressor 100via muffler cover discharge 110 and discharge line 112 for dischargingcompressed gas at high temperature for the refrigeration system.

Along the travelling passage inside the compressor 100, initially, thelow-temperature refrigerant gas is drawn into the suction muffler 104via the suction inlet pipeline 102, either directly or indirectly. Atthe entrance of the inlet pipeline 102 going into the shell 106 (point1), the gas has the lowest temperature inside the compressor shell 106,typically at about 40.5 degree Celsius. When the gas is drawn furthertowards the muffler 104, it is heated up by the surroundings totypically about 47.9 degree Celsius at the entrance (point 2) of themuffler 104. Inside the muffler 104, the gas temperature is typicallyfurther raised to about 60.3 degree Celsius (point 3) before reachingthe cylinder head 108. Further down the travelling path where the gasarrives at the suction plenum 116 of the cylinder head 108, thetemperature of the gas has typically reached about 66.9 degree Celsius(point 4). The gas is then drawn via the suction valve (not shown) to becompressed in the cylinder chamber (hidden). The compressed gas leavesvia the discharge valve (not shown) and enters the discharge plenum 114of the cylinder head 108. Inside the discharge plenum 114, thetemperature of the compressed gas is typically about 117.9 degreeCelsius (point 5). On leaving the cylinder head 108, the gas starts tocool down. Along the down stream path via muffler cover discharge 110and discharge line 112, and discharge pipeline 118 of the compressor100, the high temperature and high pressure gas typically cools to about82.8 degree Celsius at the point (point 7) where the discharge pipelineexits the shell 106.

It is evident that the gas has a large temperature difference betweenthe adjacent suction 116 and discharge plenums 114. It has beenrecognised by the applicant that the high temperature gas contained inthe discharge plenum 114 constitutes a heat source which cansignificantly contribute to the temperature increase in the lowtemperature suction refrigerant gas in the suction plenum 116 prior tocompression. The increase in the suction refrigerant gas temperaturecauses an increase in its specific volume and reduces the mass flow rateof the refrigerant gas, which in turn leads to a drop in thecompressor's efficiency due to a reduction in cooling performance. It isnoted that the high temperature compressed gas in the discharge plenum114, as well as other heat sources within the compressor structure 100,also contributes to the overall temperature increase in the suction gasas the gas travels from the inlet pipe 102 via the muffler 104 into thesuction plenum 116, which can further contribute to an overall increasein the suction refrigerant gas temperature.

FIG. 2 a shows the cross sectional view of a cylinder head 202 bolted tothe cylinder body 203. The inventors have recognized that significantheat transmission takes place between the hot gas in the dischargeplenum 204 and the gas in suction muffler 205 though the valve plate201, which is typically made from a metal. Through this the inventorshave in particular recognized that, by creating a barrier for heattransfer between the suction and discharge gas at the valve plate 201,such a valve plate structure can significantly contribute to prevent thesuction gas from being heated up. FIG. 2 b shows the resultant heat flowdiagram when a valve plate structure 210 comprising first and secondmetal plate elements 212, 214 and an inlet 215 made from an insulatingmaterial in the plate element 212 1s provided, according to an exampleembodiment. The inlet 215 functions as a thermal barrier to hinder heattransmission from the gas in the discharge plenum 216 to the gas in thesuction muffler 218. This advantageously improves the overall thermalefficiency of the compressor.

Valve plate structure 210 acts as a seal between different pressurezones within the compressor. It contains both a suction orifice 220 anda discharge orifice 222, and thus provides fluid communication of therefrigerant. It is positioned between suction reed 224 and dischargereed 226, which open when differential pressures between zones arereached and allow gases to flow from high to low pressure regions duringthe compression cycle. Due to its functional attributes, valve platestructure 210 preferably is corrosion, chemical and wear resistant, aswell as preferably being able to withstand high temperature. It alsoprovides the seal to prevent leakage of refrigerant. Preferably, thevalve plate structure 210 also allows run-time low noise and smoothmovement.

In FIG. 3, a schematic drawings of a compressor according to an exampleembodiment is shown. More particular, a cylinder head 300 is exposed toshow its interior structure and assembly. The cylinder head 300 isgenerally rectangular in shape with its four corners rounded off. At thefour corners, four equal sized apertures 308 a-d are provided forbolting, using part 309 a-d, the cylinder head 300 to the cylinder body307. Other components in the cylinder head assembly include valve platestructure 301, comprising valve plate 301 a and an insulating materialinlet 301 b, a discharge reed 302, a suction reed 303, and sealinggaskets 304, 305. A suction muffler 306 fits into the suction plenum(hidden) in the cylinder head 300. There are 2 alignment holes 310 a-bat the rim of the valve plate 301 a to provide reference guide duringassembly of the cylinder head 300 to the cylinder body 307.

FIGS. 4 to 8 show different types of valve plate structures according todifferent embodiments.

FIG. 4 shows a valve plate structure 400, comprising two plates 401 and402. Plate 401 is made of thermally insulating material, while plate 402is made of metal to provide strength. When assembled, the thermallyinsulating material plate 401 will be located towards the discharge reed(not shown). During the compression cycle, the surface of the valveplate structure 400 facing the cylinder bore (not shown) is made ofmetal, i.e. metal plate 402. This preferably prevents deformation underhigh pressure. A flat surface finish of the thermally insulatingmaterial plate 401 is preferably ensured to prevent leakage. Theflatness of the thermally insulated valve plate can be ensured throughflatness control methods such as, but not limited to, lapping. Forexample, the valve plate may be rubbed on a flat surface with anabrasive such as sandpaper there between, by hand movement or bymachine. There are protrusions 403-07 formed on plate 401 andcorresponding holes 408-12 formed on plate 402 to facilitate pressfitting of plates 401 and 402 during assembly. The cross sectional view414 shows the protrusions from plate 401 inserted in the correspondingholes in plate 402 so that plate 401 can be aligned and press fittedwith plate 402.

FIG. 5 shows a valve plate structure 500, comprising two plates 501 and502. Plate 501 is made of thermally insulating material, while plate 502is made of metal to provide strength. When assembled, the thermallyinsulating material plate 501 will be located towards the discharge reed(not shown). During the compression cycle, the surface of the valveplate structure 500 facing the cylinder bore (not shown) is made ofmetal, i.e. metal plate 502. This preferably prevents deformation underhigh pressure. A flat surface finish of the thermally insulatingmaterial plate 501 is preferably ensured to prevent leakage. Compared tothe embodiment shown in FIG. 4, there are no protrusions/correspondingholes formed the plates 501, 502, for press fitting. In this embodiment,plates 501, 502 can be assembled by for example, but not limited to,injection molding, induction heating, bonding adhesive, press fitting,ultrasonic welding etc.

FIG. 6 shows a valve plate structure 600, comprising three plates 601,602, 603. Plate 602 is made of thermally insulating material, whileplates 601, 603 are made of metal to provide strength. During thecompression cycle, the surface of the valve plate structure 600 facingthe cylinder bore (not shown) is made of metal, i.e. metal plate 603.This preferably prevents deformation under high pressure. A flat surfacefinish of the thermally insulating material plate 601 is preferablyensured to prevent leakage. In use, the metal plates 601, 603 are thusin contact with the discharge reed (not shown) and the suction reed (notshown) respectively. This preferably ensures good surface contact andprevents leakage. Also, having the surfaces adjacent the discharge andsuction reeds respectively made from metal preferably increasesreliability, for example due to the metal surface better withstandingthe reciprocating reed movements. Plates 601, 602 and 603 can beassembled by for example, but not limited to, press fitting, injectionmolding, induction heating, bonding adhesive, ultrasonic welding etc.

FIG. 7 shows a valve plate structure 700, comprising one plate 701 andan inlet 702. Inlet 702 is made of thermally insulating material, whileplate 701 is made of metal to provide strength. During the compressioncycle, the surface of the valve plate structure 700 facing the cylinderbore (not shown) is made of metal, i.e. metal plate 701. This preferablyprevents deformation under high pressure. When assembled, the thermallyinsulating material inlet 701 is inserted in a corresponding recess 704and will be located towards the discharge reed (not shown). While a flatsurface finish of the thermally insulating material inlet 702 is againpreferably ensured to prevent leakage, it will be appreciated that themajority of the surface facing the discharge reed (not shown) is made upby the surface of the metal plate 701, which preferably ensures goodsurface contact and prevents leakage. Plate 701 and inlet 702 can beassembled by for example, but not limited to, press fitting, injectionmolding, induction heating, bonding adhesive, ultrasonic welding etc. Inthis embodiment, because the regions where the screws are inserted aremade of metal, deformation under high torque, e.g. when screws (notshown) are being tightened, is preferably prevented. Also, in use, themetal plate 701 is thus in contact with both the discharge reed (notshown) and the suction reed (not shown). This preferably ensures goodsurface contact and prevents leakage. Also, having the surfaces adjacentthe discharge and suction reeds respectively made from metal preferablyincreases reliability, for example due to the metal surface betterwithstanding the reciprocating reed movements

FIG. 8 shows a valve plate structure 800, comprising two plates 801 and802. Plate 801 is made of thermally insulating material, while plate 802is made of metal to provide strength. During the compression cycle, thesurface of the valve plate structure 800 facing the cylinder bore (notshown) is made of metal, i.e. metal plate 802. This preferably preventsdeformation under high pressure. The metal plate 802 in this embodimentcomprises a raised region 803 around discharge orifice 804. Whenassembled, the raised region 803 is received in a corresponding opening805 formed in the insulating material plate 801. This preferablyenhances the reliability, for example due to the metal surface of theraised region 803 better withstanding the reciprocating reed movements.A flat surface finish of the thermally insulating material inlet 802 isagain preferably ensured. It will be appreciated that by having themetal surface of the raised region 803, in use, adjacent the dischargereed (not shown) preferably ensures good surface contact and preventsleakage and may provide improved reliability. Plates 801 and 802 can beassembled by for example, but not limited to, press fitting, injectionmolding, induction heating, bonding adhesive, ultrasonic welding etc.Also, in use, the metal plate 802 and the raised region 803 are thus incontact with the suction reed (not shown) and the discharge reed (notshown) respectively. This preferably ensures good surface contact andprevents leakage. Also, having the surfaces adjacent the discharge andsuction reeds respectively made from metal preferably increasesreliability, for example due to the metal surface better withstandingthe reciprocating reed movements

FIG. 9 shows a valve plate structure 900, with metal coatings 902, 904on both surfaces of a thermally insulating material plate 906. Thispreferably ensures good surface contact and prevents leakage. Also,having the surfaces adjacent the discharge and suction reedsrespectively made from metal preferably increases reliability, forexample due to the metal surface better withstanding the reciprocatingreed movements. Alternatively, the coating could be done on either sideof the thermally insulated valve plate. The metal coating may be formedusing various techniques understood in the art, including, but notlimited to, vapor deposition, spray coating, electroless plating.

In the example embodiments described, the thermally insulating materialmay include, but is not limited to, engineering plastics such asPolybutylene terephthalate (PBT) and Polyetherimide (PEI), LiquidCrystal Polymer (LCP), Polyether ether ketone (PEEK), PolyphenyleneSulphide (PPS) etc. The metal used in the example embodiments describedmay include, but is not limited to cast/sintered iron.

The embodiments described can provide a hybrid valve plate structure inwhich a thermal barrier provided by respective materials, of thermallyinsulating characteristics, can improve the thermal insulation such thatthe suction gas temperature in the compressor may be reduced. Since areduction in the suction gas temperature decreases its specific volumeand increases the mass flow rate of the refrigerant, this can lead toimproved compressor efficiency due to an increase in coolingperformance.

It will be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

1. A valve plate for a compressor, the valve plate having a thermallyinsulating capability for thermally insulating a suction muffler of thecompressor from a discharge plenum in a cylinder head of the compressor.2. The valve plate as claimed in claim 1, comprising a first plateelement made from thermally insulating material and a second plateelement made from metal.
 3. The valve plate as claimed in claim 2,wherein the first and second plate elements are joint by one or more ofa group consisting of press-fitting, injection molding, inductionheating, bonding adhesive, and ultrasonic welding.
 4. The valve plate asclaimed in claim 2; wherein the first plate element is disposed to facethe discharge plenum.
 5. The valve plate as claimed in claim 2, furthercomprising a third plate element made from metal, and the first plateelement is sandwiched between the first and second plate elements. 6.The valve plate as claimed in claim 5, wherein the first, second andthird plate elements are joint by one or more of a group consisting ofpress-fitting, injection molding, induction heating, bonding adhesive,and ultrasonic welding.
 7. The valve plate as claimed in claim 2,wherein the first plate element is configured to be received in a recessformed in the second plate element.
 8. The valve plate as claimed inclaim 7, wherein the recess is formed around a suction orifice in thesecond plate element.
 9. The valve plate as claimed in claim 2, whereinthe second plate element comprises a raised portion around a dischargeorifice in the second plate element, and the first plate elementcomprises an opening for receiving the raised portion.
 10. The valveplate as claimed in claim 1, comprising a first plate element made fromthermally insulating material and a metal coating on one or both sidesof the first plate.
 11. A compressor comprising a valve plate as claimedin claim
 1. 12. A method of thermal insulation applied in a compressor,comprising using a valve plate having a thermally insulating capabilityfor thermally insulating a suction muffler of the compressor from adischarge plenum in a cylinder head of the compressor.